1. Field of the Invention
The present invention relates to image encoding and decoding, and more particularly, to a color image encoding and/or decoding apparatus, method, and medium using inter-color-component prediction in accordance with an encoding mode.
2. Description of the Related Art
In video compression, generally, in order to increase the compression ratio, a color image format such as R-G-B and X—Y—Z is converted into an image format appropriate to compression, such as Y—Cr-Cb. However, when conversion to Y—Cr-Cb is performed, the quality of an image is damaged basically. Also, generally, when the Y—Cr-Cb image is compressed, the magnitudes of the Cr and Cb components are reduced approximately four times and then encoded. Accordingly, when the Y—Cr-Cb image is encoded, it is difficult to restore a high quality image close to the original image. As an example, there is a VC-1 standard technology that has been undergoing standardization recently.
As another problem, if in order to reduce this loss by the conversion into the Y—Cr-Cb format, each of the R-G-B color components is encoded independently in the conventional Y—Cr-Cb encoder. The correlation remaining between the R-G-B components must be used. Therefore, the encoding efficiency is lowered.